Modular crankshaft

ABSTRACT

In accordance with certain embodiments, a modular crankshaft features a connection system between modules that features opposed female receptacles. A pin having opposed beveled ends and hydraulic passages with it is inserted into the opposed receptacles. A pair of seals is disposed on the beveled ends and straddles a hydraulic fluid outlet. The crankshaft wall that defines each receptacle is designed to flex in response to applied hydraulic pressure between the seals on the tapered pin portion. A notch at the base of the receptacle in the crankshaft reduces stress concentration and enables the wall defining the crankshaft receptacle to come back when hydraulic pressure through the pin is removed. The opposed crankshaft receptacles are flanged to allow them to be pulled together over the pin. An interference fit results around the pin after the flanges are mated and the hydraulic pressure is removed.

BACKGROUND

The field of this invention is a crankshaft that is in modular form andmore specifically relates to a connection technique that approaches therigidity of a continuous crankshaft while allowing the flexibility to bein modular form.

Crankshafts are generally cast components that accommodate the requirednumber of throws depending on the number of cylinders in the engine orcompressor. In large compressor applications, a breakdown can be veryexpensive for the operator in the form of lost production or otherprocess outage until repairs can be made, for instance. When the repairinvolves a crankshaft, the downtime can be lengthy because vendorsseldom maintain an inventory of replacement crankshafts. Instead, when areplacement crankshaft is desired, it is manufactured from scratch,which can lead to delays and undesired downtimes.

One way to address the variety in the number of throws is to create amodular design where basic components can be assembled to each other tocreate the requisite configuration for a particular installation. Theissue that doing this raises is how to fashion a connection that will besufficiently rigid to address issues such as alignment, relativerotation and vibration, among other issues. Prior designs have attemptedto connect modules with a splined male into female connection, as isdescribed in U.S. Pat. No. 5,537,971. The problem with this design isthe bulkiness of the connection and the clearances in the splinedconnection that permit assembly but over time can wear to the point ofpermitting relative rotational movement that can cause vibration andeven spline failure, for example. Another solution is depicted in U.S.Pat. No. 4,622,864. This technique freezes a pin and inserts this frozenpin into aligned bores to put the modules together. This processrequires precise alignment of the pin to make sure that lubricationpassages through it are not obstructed. In other respects, modularshafts that attach the modules together with threads are known, as shownin a rock breaking tool in U.S. Pat. No. 4,657,306.

Therefore, there exists a need for improved modular crankshaftconnection techniques.

SUMMARY OF THE INVENTION

In accordance with certain embodiments, the present invention provides aplug with opposed tapers and spaced seal rings. Hydraulic fluid channelsrun to the tapered exterior between the seals and spread the opposingreceptacles in the adjoining modules to allow insertion of a cylindricalportion of the pin into the respective receptacles. The receptacles areconfigured to flex in response to hydraulic pressure and to return tothe original dimension when such pressure is removed, thus creating aninterference fit. The modules are then flanged together with propertorque on the flange bolts. Those skilled in the art will appreciate thevarious aspects of the present invention from a review of the exemplaryembodiments and the drawings that appear below, as well as from theclaims.

By way of example, certain embodiments of the present invention providea modular crankshaft that features a connection system between modulesthat features opposed female receptacles. A pin having opposed beveledends and hydraulic passages therein is inserted into the opposedreceptacles. A pair of seals is disposed on the beveled ends andstraddles a hydraulic fluid outlet. The crankshaft wall that defineseach receptacle is designed to flex in response to applied hydraulicpressure between the seals on the tapered pin portion. A notch at thebase of the receptacle in the crankshaft reduces stress concentrationand enables the wall defining the crankshaft receptacle to come backwhen hydraulic pressure through the pin is removed. The opposedcrankshaft receptacles are flanged to allow them to be pulled togetherover the pin. An interference fit results around the pin after theflanges are mated and the hydraulic pressure is removed.

DETAILED DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a section view of two modules joined by the attachment of thepresent invention, in accordance with an embodiment thereof;

FIG. 2 is a detailed view of the exemplary pin that is used inconnecting the modules;

FIG. 3 is an end view of the pin of FIG. 2;

FIG. 4 is a view of the pin part way into opposing receptacles on thecrankshaft modules;

FIG. 5 is a detailed view of a pin end of the pin as it is advanced intothe receptacle; and

FIG. 6 is shows the pin fully advanced as the modules are connected toeach other.

DETAILED DESCRIPTION

The exemplary modular crankshaft 10 has at least two illustrated modules12 and 14. The connection between them comprises facing end receptacles16 and 18 that receive opposed ends of a pin 20. The exemplary moduleshave flanges 22 and 24 that can be drawn together over pin 20 tocomplete the connection. The pin 20 has a system of oil passages 26through it. Details regarding the pin 20 can be better understood byreference to FIG. 2.

FIG. 2 shows the pin 20 having an inlet passage 28 connected to atransverse passage 30. Inlet passage 28 is sealed at 32, and transversepassage 30 is sealed at opposed ends 34 and 36. There are two oil outletpassages 38 and 40 that, as illustrated, are parallel to each other.However, it is worth noting that these passages may intersect and may bedisposed in the same plane or in intersecting planes. Passages 38 and 40can have one or more outlets on the outer surface 42 of the pin 20. Ends44 and 46, as illustrated, present a reduced dimension when compared tothe main portion 48 of the pin 20 that is located between them. That is,ends 44 and 46 present a frusto-conical section forming a truncatedsegment of a cone, but other shapes are contemplated. This reduceddiameter profile at ends 44 and 46 facilitates interference freeinsertion into receptacles 16 and 18, although some interference onseals 50 and 52 at one end and seals 54 and 56 at the other end iscontemplated and, in fact, desired for sealing pressure. FIG. 3 showsseals 50 and 52 on the reduced dimension portion 46. In the exemplaryembodiment, the opposed end view is the same, but the inventioncontemplates different end treatments in accomplishing the reduceddimension. With regard to the main portion 48, the receptacles 16 and 18can be similarly shaped. However, the main point is that the shapes ofthe main portion 48 and the receptacles 16 and 18 be compatible so thatthey ultimately produce an interference fit around main portion 48.Accordingly, other compatible cross-sectional shapes besides round arecontemplated.

FIGS. 4 and 5 illustrate the assembly technique in more detail. FIG. 4also illustrates exemplary circumferential recesses 58 and 60 that havea U-shaped cross-section. These recesses 58 and 60 serve to reducestress concentrations at bottoms 62 and 64 of receptacles 18 and 16 whentheir dimension is enlarged so that the receptacles will elasticallyreturn to their original dimensions around pin 20 when oil pressure isremoved, instead of plastically deforming under applied oil pressure. Asshown in FIG. 4, ends 44 and 46 have reduced dimension to allow them toreadily enter the receptacles 16 and 18. At some point of insertion,seals 50 and 52, for example, make contact with receptacle 18, while thesame result occurs at the other end of pin 20 as nut 68 is rotated onthreaded rod 66 bringing flanges 22 and 24 closer together. Bolts andnuts can be used as an alternative. FIG. 5 shows seals 50 and 52contacting receptacle 18 as oil is applied under pressure throughpassage 38. The oil under pressure elastically enlarges the dimension ofthe receptacle 18 as well as the receptacle 16 through passage 40. As aresult, the main portion 48 does not drag or only minimally contacts thesurrounding receptacle as the flanges 22 and 24 are brought togetherwith the oil pressure applied to passages 38 and 40 between seal pairsat opposed ends of the pin 20.

FIG. 6 illustrates the fully mated position of flanges 22 and 24. Itshould be noted that oil pressure is applied until the flanges mate tokeep the receptacles 16 and 18 elastically enlarged to avoid hanging thepin 20 in either receptacle. As soon as the nut 68 is torqued tospecification, the oil pressure is relieved and the presence of recesses58 and 60 facilitate the elastic return to the original dimension forreceptacles 16 and 18. The end result is that an interference fit iscreated in the zone 70 that generally corresponds to main portion 48.The modules 12 and 14 are now fully assembled. The oil line (not shown)is disconnected and capped. Those skilled in the art will appreciatethat the oil inlet connection is placed adjacent a gap in the flanges 22and 24 to allow oil access while the flanges are pulled together.Additionally, the connection described above can be undone by reversingthe process and applying oil pressure while parting the flanges 22 and24.

Those skilled in the art will appreciate that the present inventionprovides a unique way of joining modular crankshaft components forengines or compressors or other power equipment. The technique employs aresidual interference fit to better provide continuing alignment and toguard against relative rotation, without the need for splines, forinstance. The use of the oil pressure to elastically deform thereceptacles allows assembly without specialized tools and shortens thetime required for assembly. The recesses at the base of the receptacles16 and 18 mitigate against the occurrence of undesirable plasticdeformation and thus provide an interference fit of the pin 20 inreceptacles 16 and 18. Two or more modular sections that are alike orunlike can be joined in this manner to accommodate the required numberof throws or spacing desired. Pin 20 can be machined or forged.Precision instruments are not required for assembly. The exemplarymating faces 72 and 74 are precision machined so that when they arebrought together the modules 12 and 14 are properly aligned. Thepresence of the pin 20 in receptacles 16 and 18 provides the neededrigidity to the connection under load and reduces the likelihood ofdeforming or deflecting or flexing under torque to allow the modularcomponents to function as well as a unitary design. Modular componentscan now be kept on hand to handle a variety of applications withdifferent number of throws so as to reduce inventory costs and to speedup repairs regardless of the crankshaft configuration using thetechnique of modularity described above.

While the invention has been described with a certain degree ofparticularity, it is manifest that many changes may be made in thedetails of construction and the arrangement of components withoutdeparting from the spirit and scope of this disclosure. It is understoodthat the invention is not limited to the exemplified embodiments setforth herein but is to be limited only by the scope of the attachedclaims, including the full range of equivalency to which each elementthereof is entitled.

Again, the above description is illustrative of exemplary embodiments,and many modifications may be made by those skilled in the art withoutdeparting from the invention whose scope is to be determined from theliteral and equivalent scope of the claims below.

1. A modular crankshaft end connection, comprising: a first modularcomponent having a first end connection; a second modular componenthaving a second end connection; said end connections, when broughttogether, accepting a connector, without preshrinking said connector. 2.The connection of claim 1, comprising: forming an interference fitbetween said connector and at least one of said end connections.
 3. Theconnection of claim 2, wherein: at least one of said end connectionscomprises a receptacle; and said connector comprises a pin insertabletherein.
 4. The connection of claim 3, comprising: said receptacle isconfigured to be elastically enlarged.
 5. The connection of claim 4,comprising: said receptacle comprises a bottom and is formed with arecess mounted externally thereto and in general proximity to saidbottom.
 6. The connection of claim 3, wherein: said pin elasticallyenlarges said receptacle.
 7. The connection of claim 6, comprising: atleast one passage through said pin having at least one exit positionedto apply pressure to said receptacle to enlarge its dimension.
 8. Theconnection of claim 7, comprising: at least one seal adjacent said exitto direct pressure developed in said passage against the receptacle toenlarge its dimension.
 9. The connection of claim 8, wherein: said atleast one seal comprises a pair of seals that are on opposed sides ofsaid exit.
 10. The connection of claim 3, comprising: a reduceddimension on at least one end of said pin to facilitate its insertioninto a corresponding receptacle.
 11. The connection of claim 10,wherein: said reduced dimension portion comprises a taper.
 12. Theconnection of claim 10, comprising: at least one passage through saidpin having at least one exit positioned to apply pressure to saidreceptacle to enlarge its dimension; said exit located at said reduceddimension portion.
 13. The connection of claim 12, comprising: at leastone seal adjacent said exit and on said reduced dimension portion todirect pressure developed in said passage against the receptacle toenlarge its dimension.
 14. The connection of claim 13, comprising: saidat least one seal comprises a pair of seals that are on opposed sides ofsaid exit and on said reduced dimension portion that further comprises ataper.
 15. The connection of claim 3, comprising: both end connectionscomprising a receptacle and further comprising a flange adjacent anentrance to each respective receptacle connectable by at least one boltor stud; whereupon said pin is fully inserted into said receptacles,when aligned, upon said flanges being drawn together by said bolt orstud.
 16. The connection of claim 15, comprising: said receptacles areexpanded as they are drawn over said pin.
 17. The connection of claim16, comprising: said pin comprises opposed reduced dimension endsegments to facilitate initial insertion into opposed receptacles. 18.The connection of claim 17, comprising: said pin comprises conduitshaving exits at said reduced dimension segments to facilitate pressuretransmission to the receptacles to expand them to the point of allowinga larger main portion of the pin to pass into said receptacles withoutinterference.
 19. The connection of claim 18, comprising: sealsstraddling exits of said conduits in said reduced dimension segments toallow pressurizing and flexing said receptacles as they are advancedover said pin.
 20. The connection of claim 19, comprising: said largermain portion of said pin conforming to the shape of a surroundingreceptacle but having a larger dimension than said receptacle beforesaid receptacle is elastically enlarged such that upon removal ofpressure through said conduits an interference fit is formed on saidmain portion in said receptacles; said first and second end connectionsfeature a recess mounted exterior to each receptacle to facilitateexpansion in the elastic range when pressure is applied in saidconduits.
 21. A modular crankshaft end connection, comprising: a firstcrankshaft having a receptacle at one end; a coupling member having achannel extending therethrough and having first and second portions,wherein the cross-sectional diameter of the first portion is larger thanthe parallel cross-sectional diameter of the second portion, and thecoupling member includes a outlet port in fluid communication with thechannel and located between first and second portions; and a sealingassembly configured to circumscribe the coupling member between theoutlet port and the first portion, and configured to sealing engage withthe receptacle when the coupling member is inserted into the receptacle.22. A modular crankshaft end connection, comprising: first and secondcrankshafts, each having a receptacle at one end; a pin at leastpartially received by the receptacles and having at least one channelextending therethrough, wherein the channel is in fluid communicationwith the receptacles of the first and second crankshaft; a plurality ofsealing members disposed about the pin and configured to sealinglyengage with the receptacles.